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Home > Bleeding Disorders > Hemophilia A and B > The treatment of hemophilia > Factor replacement therapy
Factor replacement therapy
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What is factor replacement therapy? What are the advantages of today's factor concentrates? How are factor VIII and IX concentrates made? What are the blood products of choice for hemophilia A? What are the blood products of choice for hemophilia B? How often are factor concentrates given? What is prophylaxis therapy vs. on-demand therapy? Are these blood products effective in stopping bleeding? Is factor replacement therapy always necessary for bleeds?
What is hemophilia
What is factor replacement therapy?
The history of hemophilia
The basic treatment to stop or prevent bleeding in people with hemophilia A and B is factor replacement therapy. This is the infusion (injection into the bloodstream) of factor VIII and IX concentrates to prevent or control bleeding.
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These concentrates come from two sources: human plasma (a component of blood) or a genetically engineered cell line made by DNA technology, called recombinant. In both cases, the factor VIII or IX protein is nearly identical to the protein which is lacking in the blood of hemophiliacs. After an infusion of the concentrate, all the proteins needed for clotting are in place. A hemophiliac's blood becomes 'normal', at least for a few hours. This allows the time for a clot to form at the site of the damaged blood vessel. (See The clotting problem in hemophilia.) Unfortunately, the replacement of the missing clotting factors is not permanent. Half of the clotting factor activity which was infused is removed by the body every 12 to 24 hours. This means that within 2 or 3 days almost none is left. The hemophiliac's blood is again unable to clot normally.
What are the advantages of today's factor concentrates? The clotting factors available in Canada today have many advantages over products available in the 1950s, 1960s, 1970s and 1980s. (See The history of hemophilia.) These are the advantages. They are very concentrated. This means that a small amount contains enough factor VIII or IX activity to control bleeding, even in major surgery. Thus, they are very effective. They are convenient. The concentrates can be stored in a home refrigerator for up to a year or kept at room temperature for 3 to 12 months. They are easy to mix. A small amount of sterile water, about 5 to 10 millilitres, is mixed with the powdered concentrate. A few seconds to one minute later the preparation is ready to be infused. They are quick to infuse. From beginning to end, the infusion takes no more than 15 to 20 minutes. They are very safe. None of the factor VIII or IX concentrates, whether plasma-derived or recombinant, used in Canada since 1988 have ever transmitted HIV or hepatitis.
How are factor VIII and IX concentrates made? Factor VIII and IX concentrates can be divided into two categories: recombinant, genetically engineered factor VIII and IX plasma-derived factor VIII and IX. Recombinant, genetically engineered factor VIII and IX Recombinant, genetically engineered factor VIII and IX are not made from human plasma. They are made like this. The human factor VIII (or IX) gene is isolated through genetic engineering. The gene contains the code which has instructions for the cell on how to make human factor VIII (or IX). The gene is inserted into non-human cells, such as baby hamster kidney cells or Chinese hamster ovary cells. These cells are grown in a cell culture. They produce factor VIII (or IX). The factor VIII (or IX) is separated from the cell culture and purified. Sucrose is then added to stabilize the final factor VIII (or IX) product. Plasma-derived factor VIII and IX Plasma-derived factor VIII and IX are made from human plasma. Plasma donations are pooled together in a pharmaceutical plant. Then, the plasma is separated into different products. This is called fractionation. The main products are: albumin (to treat burns) immune globulins (to treat problems of the immune system) factor VIII (to treat hemophilia A) factor IX (to treat hemophilia B). The plasma-derived clotting factor concentrates available in Canada have an excellent safety record - no cases of transmitting HIV, hepatitis B or C. Plasma-derived blood products go through four separate safety steps. Each blood donor is questioned each time he / she gives blood to find out if he / she has a greater than normal risk of carrying a blood-borne virus. If the person has a risk factor, he / she is not allowed to donate. Each blood donation is tested for known pathogens, for example: HIV, hepatitis B and hepatitis C. If a blood donation tests positive, it is not used. The donor can no longer donate blood. After the plasma is pooled, the plasma is again tested for known pathogens. If the plasma pool contains any trace of contamination, it is discarded. After manufacture, the final product undergoes a viral inactivation process. This is to kill any viruses which might be in the blood product. Methods of viral inactivation are: heating the clotting concentrate with vapour heat, treating the clotting concentrate with solvent detergents and nano-filtering. These viral inactivation methods are very effective in killing HIV, hepatitis B and C.
What are the blood products of choice for hemophilia A? Genetically engineered (recombinant) factor VIII is the clotting factor concentrate used by most Canadians with hemophilia A. It has been the product of choice since being introduced in 1993. The brand names used in Canada are Advate ®, Kogenate ®FS and Xyntha ®. In Quebec, Eloctate ®, an extended half-life product, was introduced in 2015 for patients with specific needs. Plasma-derived factor VIII is sometimes used in particular situations for the treatment of hemophilia A: 1) for previously untreated patients who may be at higher risk for the development of inhibitors and 2) for immune tolerance induction for patients who have already developed antibodies to factor VIII. Brand names used in Canada are Humate P® and Wilate ®.
What are the blood products of choice for hemophilia B? Recombinant factor IX, which goes under the brand name of Benefix ® is the blood product used by most Canadians with hemophilia B. It was introduced in Canada on a regular basis in 1998. In Quebec, Alprolix TM, an extended half-life product, was introduced in 2015 for patients with specific needs. Plasma-derived factor IX is also used by Canadians with hemophilia B. The brand name used in Canada is ImmunineVH ®.
How often are factor concentrates given? Depending on the person, factor concentrates are given: every day several times a week several times a month only in cases of an accident or surgery or almost never. The hemophiliacs who receive factor concentrates the most often are: severe hemophiliacs children who are very active hemophiliacs on prophylaxis therapy.
What is prophylaxis therapy vs. on-demand therapy? In prophylaxis therapy, hemophiliacs receive factor concentrates one or more times a week to prevent bleeding. The goal is to keep the levels of factor VIII or IX in the blood high enough that bleeding does not happen. This therapy is common with children with severe hemophilia. On-demand therapy is the infusion of factor concentrates immediately after the beginning of a bleed. The goal is to stop the bleeding quickly, before any damage is done to the joint or muscle. Research has shown that prophylaxis therapy gives children the best chance to reach adulthood without damage to their joints.
Are these blood products effective in stopping bleeding? Yes, for most hemophiliacs, factor concentrates are very effective in stopping bleeding. Hemophiliacs can even have major operations without bleeding more than a person whose blood is normal. However, some hemophiliacs' bodies reject the infusions of factor concentrates. They develop inhibitors. Inhibitors are the body's way of fighting off what it sees as a foreign agent. This means that as soon as the coagulation factor is injected, it is eliminated. This often happens before the factor concentrate is able to do its work and stop the bleeding. Fortunately, there are ways to help most hemophiliacs who have inhibitors. (See The complications of hemophilia.)
Is factor replacement therapy always necessary for bleeds? No. Minor bleeding episodes associated with hemophilia sometimes do not require medical treatment. For example: small bruises usually disappear on their own bleeding from minor cuts can be stopped by applying pressure very minor bleeding into tissues can sometimes be treated by : rest elevation of the limb applying ice to the site of the bleed. Bleeding into a joint or a muscle (especially around the hip, calf or forearm) is never minor. Treatment with factor concentrates is essential. Doctors say, 'When in doubt, infuse. Ask questions later.' Links
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